1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an inductive-type magnetic transducer for writing and to a method of manufacturing the same.
2. Description of the Related Art
In recent years, improvements in the performance of a thin-film magnetic head are sought since a surface recording density of a hard disk device has been improved. A composite thin-film magnetic head having a structure, in which a recording head having an inductive-type magnetic transducer for writing and a reproducing head having a magnetoresistive (hereinafter referred to as MR) element for reading are stacked, is widely used as the thin-film magnetic head.
A factor that determines the performance of the recording head is accuracy in processing a throat height (TH). The throat height is a length (height) of a portion (magnetic pole portion) between an air bearing surface and an edge of an insulating layer which electrically isolates a thin-film coil. The air bearing surface, here, is a surface of the thin-film magnetic head facing a magnetic recording medium, and is also called a track surface. A reduction in the throat height is desired in order to improve the recording head performance. The throat height is controlled by an amount of polishing in processing the air bearing surface.
In order to improve the performance of the thin-film magnetic head, the above recording head and the reproducing head must be formed in a good balance.
A method of manufacturing a composite thin-film magnetic head is described with reference to FIGS. 42A and 42B to FIGS. 48A and 48B as an example of the thin-film magnetic head of the art related to the present invention. FIG. 49 is a plan view of the composite thin-film magnetic head of the art related to the present invention. FIG. 42A to 48A each illustrate a manufacturing step taken along the line XLVIIIAxe2x80x94XLVIIIA in FIG. 49, while FIG. 42B to 48B each illustrate a manufacturing step taken along the line XLVIIIBxe2x80x94XLVIIIB in FIG. 49.
First, as shown in FIG. 42A and FIG. 42B, an insulating layer 102 made of, for example, alumina (aluminum oxide: Al2O3) of about 5 xcexcm in thickness is formed on a substrate 101 made of, for example, Altic, i.e., aluminum oxide and titanium carbide (Al2O3 with TiC). A bottom shield layer 103 for a reproducing head is formed of, for example, permalloy (NiFe) on the insulating layer 102.
As shown in FIGS. 43A and 43B, a shield gap film 104 is formed on the bottom shield layer 103 by depositing, for example, alumina in thickness of 35 nm to 60 nm. An MR film 105 of tens of nanometers in thickness for making up the MR element for reproduction is formed on the shield gap film 104, and a desired shape is obtained through photolithography with high precision. Next, a pair of lead terminal layers 106 are formed by a lift-off method on both sides of the MR film 105. A shield gap film 107 is formed on the shield gap film 104, the MR film 105, and the lead terminal layers 106, so that the MR film 105 and the lead terminal layers 106 are buried between the shield gap films 104 and 107. Further, as shown in FIG. 43A and FIG. 43B, a top-shield-cum-bottom pole (or a bottom magnetic layer; hereinafter referred to simply as a bottom pole) 108 having a thickness of 2.5 xcexcm to 3.5 xcexcm and made of a magnetic material, such as permalloy, used for both reproduction and recording heads, is formed on the shield gap film 107.
As shown in FIG. 44A and FIG. 44B, a write gap layer 109 made of, for example, an alumina film and having a thickness of 200 nm to 250 nm is formed on the bottom pole 108. The write gap layer 109 is patterned through photolithography, to thereby form an opening 109a for magnetically connecting the bottom pole 108 and a top pole (or a top magnetic layer; hereinafter referred to simply as a top pole) 113 to be formed thereon in a later step. A photoresist film 110 as a first layer of photoresist films of 1.0 xcexcm to 1.5 xcexcm in thickness is formed on the write gap layer 109, and the photoresist film 110 is then processed to a prescribed pattern through high-precision photolithography. The purpose of providing the photoresist film 110 is to improve insulation capability between the bottom pole 108 and a thin-film coil 111 to be formed on the photoresist film 110 in a later step.
As shown in FIG. 45A, the thin-film coil 111 for an inductive recording head made of, copper (Cu) and having a thickness of 1.5 xcexcm to 2.0 xcexcm is selectively formed on the photoresist film 110 by, for example, electroplating.
Next, as shown in FIG. 46A, a photoresist film 112 of, for example, 1.0 xcexcm to 1.5 xcexcm in thickness is formed on the thin-film coil 111, and the photoresist film 112 as a second layer of photoresist films is patterned to a prescribed shape through photolithography with high precision. The photoresist film 112 is subjected to a predetermined heat treatment, so as to planarize the surface and improve insulation capability between the thin-film coil 111 and the top pole 113 which will be formed on the photoresist film 112 in a later step. This kind of photoresist film 112 can achieve surface planarization regardless of the surface irregularity of the underlayer, and can also provide a very gentle slope at the edge (peripheral area) of the photoresist film 112 by performing heat treatment after patterning to gradually change the thickness of the film.
An end (or edge) of the second photoresist film 112 shown on the left hand side in FIG. 46A corresponds to the reference position for determining the throat height (TH), i.e. the throat height zero (TH0) position. As shown in this figure, a side surface of the photoresist film 112 located on the above edge side can effectively determine an apex angle. The apex angle is an angle xcex8 between the tangent line to an end surface of the photoresist film 112 on the track surface (air bearing surface) 100 side and an upper surface of the top pole 113 to be formed in a later step (or the surface of the substrate 101).
The apex angle (angle xcex8) formed by the gentle slope of the second photoresist film 112 can be reduced to about 25 degrees to 35 degrees by setting the distance between the throat height zero (TH0) position and the position of the side surface of the outermost periphery portion of the thin-film coil 111 to, for example, 10 xcexcm. In other words, when the bottom pole 108, the write gap layer 109, and the top pole 113 are patterned through photolithography to define the recording track width in a later step, a relatively small apex angle allows such patterning to be performed on planarized regions, so that patterning accuracy can be improved and therefore the narrower track can be realized.
As shown in FIG. 47A, a top yoke-cum-top pole 113 of 2.0 xcexcm to 3.0 xcexcm in thickness is formed of a magnetic material for the recording head, such as permalloy, on the photoresist film 112. The top pole 113 has, for example, such a plan shape as shown in FIG. 49, which will be described hereinafter. As shown in FIG. 49, the top pole 113 has a top pole tip portion 113a having a width corresponding to the track width on the track surface (air bearing surface) 100 side. As shown in FIG. 47A and FIG. 47B, the top pole tip portion 113a of the top pole 113 faces part of the bottom pole 108 located on the track surface (air bearing surface) 100 side with the write gap layer 109 in between. The top pole 113 has contact with the bottom pole 108 through the opening 109a, magnetically coupled thereto.
As shown in FIG. 48B, the write gap layer 109 and the bottom pole 108 are partially etched by about 0.3 xcexcm to 0.4 xcexcm by ion milling etching using the top pole tip portion 113a of the top pole 113 as a mask. By etching as far as the bottom pole 108 to form a trim structure, the effective writing track width can be made small, to thereby prevent divergence of magnetic flux at the bottom pole 108 during data writing operation.
As shown in FIG. 48A and FIG. 48B, an overcoat layer 114 is formed of, for example, alumina on the top pole 113. The thin-film magnetic head is completed after the track surface (air bearing surface) 118 of the recording head and reproducing head is formed by applying machine grinding with a slider.
The thin-film magnetic head of this type is expected to have the surface recording density of as high as 10 gigabits to 20 gigabits per square inch, and to be used in a high frequency band of 300 MHz to 500 MHz in the near future. Therefore, how to ensure an optimum magnetic volume in the vicinity of the throat height (TH) zero position is becoming an important task. Naturally, the overwrite characteristics can be improved if a large magnetic volume can be obtained in the vicinity of the throat height (TH) zero position.
As shown in FIG. 46A and FIG. 49, the throat height (TH) zero position is effectively determined by the second photoresist film 112. The photoresist film 112 is provided with a very gentle slope, which cannot be obtained by, for example, patterning an alminum film, a silicon oxide film or a silicon nitride film each formed through sputtering. Therefore the top pole 113 can also be formed on the photoresist film 112 in a gently-sloped shape in the vicinity of the throat height (TH) zero position, along the surface shape of the photoresist film 112. As shown in FIG. 49, the width of the pole is gradually reduced from the top pole 113 on the thin-film coil 111 toward the top pole tip portion 113a (the throat height (TH) zero position) on the write gap layer 109, so that magnetic volume can be gradually reduced and the magnetic flux can be converged in an efficient manner. Additionally, by gradually varying the distance between the top pole 113 and the write gap layer 109 as described above, the magnetic flux in the top pole 113 can be converged even more smoothly.
In addition, since the second photoresist film 112 can be formed with a very gently sloped surface to thereby reduce the apex angle, processing accuracy in photolithography forming the trim structure can be improved, to thereby achieve a narrow track width.
However, in contrast to the advantage of providing the second photoresist film 112 with a very gently sloped surface, the thickness of the film is made extremely thin in the vicinity of the throat height (TH) zero position. As a result, magnetic flux is often leaked between the top pole 113 and the bottom pole 108 in the area where the photoresist film 112 has a small thickness (in the vicinity of the throat height (TH) zero position).
The present invention has been conceived in view of the above-described problems, and effectively resolves the problems caused by employing a non-magnetic body such as the above-described second photoresist film 112 having a very gentle slope. More specifically, it is a first object of the present invention to provide a thin-film magnetic head and a method of manufacturing the same that allow an optimum control of magnetic flux flowing in the vicinity of the throat height zero (TH0) position and effective prevention of magnetic flux leakage between the top pole and the bottom pole in the vicinity of the throat height zero (TH0) position.
It is a second object of the present invention to provide a thin-film magnetic head and a method of manufacturing the same that achieve the above first object and allow improvement in overwrite performance.
It is a third object of the present invention to provide a thin-film magnetic head and a method of manufacturing the same that allow at least one of the first and second objects to be achieved with a simple structure or by a simple manufacturing method.
It is a fourth object of the present invention to provide a thin-film magnetic head and a method of manufacturing the same that allow reduction in manufacturing steps and achievement of at least one of the first, second, and third objects.
A thin-film magnetic head of the invention includes a first insulating layer as a write gap layer, a non-magnetic body provided adjacent to a surface of the first insulating layer in an area close to an air-bearing surface that faces a recording medium and having a wedge-shaped cross section that is taken along a surface perpendicular to both a surface along which the first insulating layer extends and the air-bearing surface, the wedge-shaped cross section directing its tip to the air-bearing surface, a bottom magnetic layer and a top magnetic layer facing each other on a side close to the air-bearing surface, sandwiching the first insulating layer therebetween and magnetically coupled to each other on a side far from the air-bearing surface, the bottom magnetic layer including a bottom pole provided so as to be exposed to the air-bearing surface and to face the first insulating layer, a bottom pole tip portion provided in an area between the bottom pole and the first insulating layer on the side close to the air-bearing surface, the bottom pole tip portion being exposed to the air-bearing surface and adjacent to both the bottom pole and the first insulating layer, and a bottom magnetic connection portion provided adjacent to the bottom pole in the area between the bottom pole and the first insulating layer on the side far from the air-bearing surface, and the top magnetic layer including, a top pole provided so as to be recessed from the air-bearing surface and to face the first insulating layer, a top pole tip portion provided in an area between the top pole and the first insulating layer on the side close to the air-bearing surface, the top pole tip portion being exposed to the air-bearing surface and adjacent to both the top pole and the first insulating layer, the top pole tip portion facing the bottom pole tip portion sandwiching the first insulating layer therebetween and extending over the non-magnetic body, and a top magnetic connection portion provided so as to magnetically couple the top pole to the bottom magnetic connection portion, a first thin-film coil buried with a second insulating layer in an area enclosed by the first insulating layer and the bottom magnetic layer, and a second thin-film coil buried with a third insulating layer in an area enclosed by the first insulating layer, the non-magnetic body and the top magnetic layer, wherein the top pole tip portion and the third insulating layer constitute a flat plane and the top pole is provided on the flat plane and a concave portion is provided close to the second insulating layer in the bottom pole tip portion and a part of the second insulating layer is buried in the concave portion adjacent to the first insulating layer.
The present invention also provides a method of manufacturing a thin-film magnetic head including the steps of forming a first insulating layer as a write gap layer, forming a non-magnetic body in an area close to an air-bearing surface that faces a recording medium in a manner that the non-magnetic body is provided adjacent to a surface of the first insulating layer and has a wedge-shaped cross section that is taken along a surface perpendicular to both a surface along which the first insulating layer extends and the air-bearing surface, the wedge-shaped cross section directing its tip to the air-bearing surface, forming a bottom magnetic layer and a top magnetic layer so as to face each other on a side close to the air-bearing surface, sandwiching the first insulating layer therebetween and to be magnetically coupled to each other on a side far from the air-bearing surface, the bottom magnetic layer including, a bottom pole provided so as to be exposed to the air-bearing surface and to face the first insulating layer, a bottom pole tip portion provided in an area between the bottom pole and the first insulating layer on the side close to the air-bearing surface, the bottom pole tip portion being exposed to the air-bearing surface and adjacent to both the bottom pole and the first insulting layer, and a bottom magnetic connection portion provided adjacent to the bottom pole in the area between the bottom pole and the first insulating layer on the side far from the air-bearing surface, and the top magnetic layer including, a top pole provided so as to be recessed from the air-bearing surface and to face the first insulating layer, a top pole tip portion provided in an area between the top pole and the first insulting layer on the side close to the air-bearing surface, the top pole tip portion being exposed to the air-bearing surface and adjacent to both the top pole and the first insulating layer, the top pole tip portion facing the bottom pole tip portion sandwiching the first insulating layer therebetween and extending over the non-magnetic body, and a top magnetic connection portion provided so as to magnetically couple the top pole to the bottom magnetic connection portion, burying a first thin-film coil with a second insulating layer in an area enclosed by the first insulating layer and the bottom magnetic layer, and burying a second thin-film coil with a third insulating layer in an area enclosed by the first insulating layer, the non-magnetic body and the top magnetic layer, wherein the top pole tip portion and the third insulating layer constitute a flat plane and the top pole is formed on the flat plane and a concave portion is provided close to the second insulating layer in the bottom pole tip portion and a part of the second insulating layer is buried in the concave portion adjacent to the first insulating layer.
In the thin-film magnetic head of the invention, the non-magnetic body, provided adjacent to a surface of the first insulating layer in an area close to an air-bearing surface that faces a recording medium, can suppress leakage of magnetic flux between the two magnetic layers facing each other with the write gap layer in between. The non-magnetic body has a wedge-shaped cross section taken along a surface perpendicular to both of the above flat surface and the recording-medium-facing surface, with its tip facing the recording-medium facing surface side. In addition, the non-magnetic body has a surface in the form of a gentle slope having a gradually increasing thickness.
In the thin-film magnetic head and the method of manufacturing the same of the invention, the non-magnetic body is preferably formed of any of the photoresist film, an organic spin-on-glass film, and an inorganic spin-on-glass film having a gentle slope.
In the thin-film magnetic head and the method of manufacturing the same of the invention, the second insulating layer is preferably formed of any of the photoresist film, an organic spin-on-glass film, a silicon oxide film, a silicon nitride film, and an alumina film.
In the thin-film magnetic head and the method of manufacturing the same of the invention, the non-magnetic body and second insulating layer may be formed as separate bodies by separate steps.
In the thin-film magnetic head and the method of manufacturing the same of the invention, the first and second non-magnetic bodies may be formed by the same step.
In the thin-film magnetic head and the method of manufacturing the same of the invention, the second non-magnetic body may be simultaneously formed by the step of forming the insulating layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.